1. Technical Field
The present invention relates to photoreceptor devices, liquid crystal apparatuses including photoreceptor devices, and electronic apparatuses including photoreceptor devices.
2. Related Art
Photoreceptor devices that detect illuminance of ambient light have been available. Such a photoreceptor device includes, for example, a photoelectric converter element and an illuminance detecting circuit.
The photoelectric converter element converts received ambient light into an electric signal and outputs the electric signal. The magnitude of the electric signal changes according to the amount of ambient light received by the photoelectric converter element. That is, the magnitude of the output electric signal becomes larger as the amount of ambient light received becomes larger, and the magnitude of the output electric signal becomes smaller as the amount of ambient light received becomes smaller.
The illuminance detecting circuit detects an illuminance of ambient light on the basis of the magnitude of the electric signal output from the photoelectric converter element. More specifically, the illuminance detecting circuit measures the magnitude of the electric signal output from the photoelectric converter element, and determines the amount of ambient light received by the photoelectric converter element such that the amount of ambient light becomes larger as the magnitude of the electric signal becomes larger and the amount of ambient light becomes smaller as the magnitude of the electric signal becomes smaller. Then, the illuminance detecting circuit detects an illuminance of ambient light on the basis of the amount of ambient light that has been determined.
Such a photoreceptor device is provided, for example, in a liquid crystal apparatus. Such a liquid crystal apparatus is described, for example, in JP-A-2005-121997. The liquid crystal apparatus described in JP-A-2005-121997 includes a liquid crystal panel, and a backlight that is provided opposing the liquid crystal panel and that emits light toward the liquid crystal panel.
The liquid crystal panel includes a pair of substrates and liquid crystal provided between the pair of substrates. The liquid crystal panel has a pair of electrodes, and driving voltages are applied to the liquid crystal via the pair of electrodes to change the orientation or order of the liquid crystal. This causes variation in the amount of light transmitted from the backlight through the liquid crystal, whereby multi-level display is achieved.
The visibility of display on the liquid crystal apparatus changes depending on the ambient illuminance of the liquid crystal apparatus, which is attributable to ambient light, such as sunlight. That is, as the ambient illuminance of the liquid crystal apparatus increases, the difference between the ambient illuminance of the liquid crystal apparatus and the illuminance of a display area of the liquid crystal apparatus decreases, so that the visibility of display on the liquid crystal apparatus is reduced.
In order to alleviate this problem, the illuminance of ambient light is detected by the photoreceptor device described above, and the amount of light emitted from the backlight is controlled on the basis of the detected illuminance of ambient light. Thus, the amount of light supplied from the backlight toward the liquid crystal panel is controlled on the basis of the ambient illuminance of the liquid crystal apparatus, so that the visibility of display on the liquid crystal apparatus is improved.
The characteristics of the photoelectric converter element included in the photoreceptor device gradually change as ambient light is received or time elapses during the operation of the liquid crystal apparatus. When the characteristics of the photoelectric converter element change, the magnitude of the electric signal output from the photoelectric converter element changes even when the amount of ambient light received is the same. Thus, an error could occur in the illuminance of ambient light detected by the photoreceptor device.